Graphic recording



.Lam 6, 1953 c, F. CARLSON GRAPHIC RECORDING 5 sheets-Sheet 1 Filed Oct. ll, 1944 KRIMI Jan. 6, 1953 c, F. CARLSON 2,624,652

` GRAPHIC RECORDING Filed Oct. 1l, 1944 3 Sheets-Sheet 2 A [STR/C /ND/C/q T/NG METERS IN VEN TOR.

Jan. 6, 1953 C, F CARLSON 2,624,652

' GRAPHIC RECORDING Filed OGC. ll, 1944 K 3 htS-Sheet 5 INVEN TOR.

Patented Jan. 6, 1653 UNITED STATES PATENT OFFICE GRAPHIC RECORDING Chester F. Carlson, New York, N. Y.

Application October 11, 1944, Serial No. 558,252

5 Claims. 1

This invention relates to electrographic recording and particularly to methods f recording data utilizing a process of electrophotography such as that described in Carlson Patent 2,297,691, granted October 6, 1942.

An object of the invention is to improve graphic recording methods and apparatus, and recording meters.

Another object is to improve electrophotography and methods and apparatus associated therewith.

Other objects will be apparent from the following description.

In the drawings:

Figure l is an elevation, partly in section, of an electrographic recording meter;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a detail of the drive for the dusting device for the meter;

Figure 4 is a detail of a modified electrophoto cylinder, carrying a scale;

Figure 5 is a fragmentary sectional view of a modied recording meter;

Figure 6 is a sectional elevation of a further modified meter;

Figure 7 is a section on line 'I-I of Figure 6;

Figures 8 and 9 show fixing chambers for xing an electrographic image; and

Figure 10 illustrates a recording made according to the method herein described.

Carlson Patent 2,297,691 describes a process of electrophotography wherein a layer of photoconductive insulating material is given an electrostatic charge on its surface and then exposed to a light image while it is supported on a ccnductive backing to thereby discharge part of the charge leaving an electrostatic latent image which is then developed by dusting with a fine powder. The powder may then be transferred by contact to a sheet of paper or other surface and fixed thereon. The present invention contemplates graphic recording meters for recording metric data, embodying this process. It also contemplates improved methods and apparatus for performing parts of the electrophoto process, such as devices for applying the dusting powder to the electrophoto plate, and devices for fixing the powder image onto paper or other surfaces. These devices are useful in electrographic recording generally as well as in graphic recording meters.

Figure 1 shows a recording meter for producing a graphic record on a strip of paper tape of the position of the moving element or pointer of one or more indicating instruments, such as ammeters, voltmeters, galvanometers, hygrometers, pressure gauges and a variety of other signal or condition indicating devices. The meter comprises a casing I0 within which is mounted a galvanometer II (for example) having a small mirror I2 mounted cn its armature shaft. A small shielded incandescent lamp I3 is mounted to illuminate the mirror. The light beam is reflected by the mirror onto the surface of a rotating cylinder I4 having a coating I5 of photoconductive insulating material thereon.

The axis of the armature is perpendicular to the axis of the cylinder so that as the armature swings on its pivots, the spot of light projected by the mirror onto the cylinder surface will move across the surface in a path parallel to the cylinder axis.

Cylinder I4 is driven at a constant speed by gear train I6 (Figure 2) from a power source. As it rotates in a clockwise direction as viewed in Figure 1 it passes a series of stations at which separate operations take place. At the first of the stations it passes under a charging belt I1 which comprises a plush covered belt running on a pair of flanged pulleys I8, one of which is driven by a small electric motor I9. The plush surface of the belt is in frictional contact with the coating I5 across the cylinder surface, so that a frictional electrostatic resident charge is uniformly applied to the coating as it passes under the belt and a strong electric field is thereby created through the layer.

As the drum surface at the second station passes the light beam reflected from the mirror I2, the spot of light falling on the photoconductive insulating coating I5 will discharge the resident electrostatic charge in a path which the spot describes on the drum surface as' it rotates. As the galvanometer armature moves, the position of the light spot will change so that the line it describes on the drum will correspond to the curve of a graph.

A dusting device is mounted at the third station, which is adjacent the drum surface below the exposure position. This comprises a chamber 20 having a window 2I open to the drum surface. A rotating cylinder 22 having a grooved surface is mounted in the bottom of the chamber 20 and a round rotating brush 23 is mounted along its side to throw dust from the cylinder surface into the air of the chamber. A powder supply bin 24 is mounted beside the chamber and has a slit at its bottom communicating with chamber 20 adjacent the drum 22. As the drum rotates it carries powder at a constant ,accesos rate from chamber 2S and bin 2Q to the brush 23 which sprays it into the air of the chamber. An adjustable baiile 25 affords a means for varying the circulation of air in the chamber to carry more or less powder near to the charged surface o1" coating I5 where it can be captured by the electrostatically charged surface. This produces a powder coating on the charged areas of coating 4i5, but the path where the coating has beendischargedfby the light "beam remains bare.

Rotating brush 23 is driven by an electric motor 26 as shown in Figure 3 and drum 22 is also driven by the motor through an adjustable'speed reducer 21 having a lever 28 for adjusting the speed of roll 22 to control the rateV of-powder supply to the brush 23. y

Powder 29 may be any colored or white electroscopic powder such as a finely divided resin, Vinsol, ethyl cellulose or the like, dyed zein pbwderl" ori' otherorganio or inorganic` composition?- Tliepreferred" powderv has' spherical prticlsles'sthan one1 mil'in' diameter: Itis desirableV that it4 be' either thermoadhesiveC or solublefin organic solvents for xin'gi purposes; as willfbe described' later:

sft pressureroller llis' mounted' atthe four-th station directly beneath cylinder ifi to rll a strip 'of paper tape 3| against the powdercariyingi'surface; The' paper 3l is"v fed fromV a roll 32 mountedi`iri"a;;casing'33: Itis desirable tlia't'fthepaperbe'kept slightly damp with water or-y other' liduid to" facilitate transfer of the powder-'itc the 'paper'and amoist pad'tfin casing 33`fh`elps`to keep th'e'paper in moist condition;

Asthel paper temergesfrom b'etween`roll 35i and cylinder I4 it is drawn over the surfaceof Ietallpl'ate 35" and'. down between' twoA tension rollers- 39.' A gri'df of electrically heated'wires 31 i mounted"in'a'housing'closely adjacent to tlesurface Tof" the paper as it'zpasses-l over plate 35 tofuseithe transferred 'powder-'onto 'the paper, thereby "producing" a permanent g'i'aphici record. 'Ile cold plate 357^ protects' the paper' from over liealtirig*during? fusion of the powder.

"l'hef'color of paper 3 l" should be in contrast totha't ofpowder 291th render'thegraph visible; (With Yheat fixing itis necessary that the powder beftherioadhesive; A'solvent fixing method 'will befdescri'bed lat'e'rr) Mstfof thef powdertransferred from the coating l to paper 3`I/b'ut'asmal1famount're; mains? This'lis removed-at the fth stationby brushesfor plush covered 'bars' 3'8rl'ield by springs 3lf against `the surfac'eof the cylinder, the eX- cefs's powder' fallingVv into: trough 69; at' the left of" tlieilm'achineas; seen in Figure- 1; A: glass window 4| in=the casing" lpermits'f'visual-i inspectiorlfof the'condi'tion ofthe coatingf l5.-

To reduce humidityy effects itI isdesirable that the cylinderA libe kept ata'temperature' slightly above the surroundings. For this purpose a pair ofm'etalencased resistance heating elements i2 arefsmounted inV heat transfer relation to the endsT of cylinder I4.

For graphicy recording it is usually necessary for some sortof scale or indicia to be printed onA ther chart In the present device this can be: printed on the paper tape inadvance but greater accuracy in the record willbeobtained iflthe scale or rulings-are applied .to the cylinder |4-.- Figure l shows one means for producing 11h-escale'. A metal cylinder Ilia is used which has its surfacev cut or'etched` to provide raised .scalefridgest Aand indicia 44. The coating: of

4 photoconductive insulating material [im is filled in between the ridges so that the final surface of the drum is a smooth cylinder, the metal ridges and indicia being exposed. Since the metal will not hold an electrostatic charge the rulings thus provided will not attract the powder and so will be in contrast to the charged areas of coating ld.

It is also possible to make a scale optically on th'e: coating; during; recording. Figure 1 shows a light projector' 1154 forprojeoting an image of a lament or a slit onto the coating i5 near one edge. The light source may be controlled either directly or by an electromagnetic shutter to project the image onto the plate atI'intervalsdetermined by a timer or according to anyw other. desired measuring factor, thereby producinga recordof that factor along the edge or centenof the graph. If desired the projector i5 may project a row of light spots at spaced points across` the drum surface. These. will.. describe. lines as the drum..rotates.y

Figurer` pshowsa4 modification of. part oith'e apparatus to. produce: an electrostatic. dustdefposit on the graph line insteadofon. theback.- ground.1 In this. case the charging.; belt..at.the first station is. replacedfby a. lamp.. ilwhicliin.- sures that theph'otoconductive coating. iisconi.- pletely. discharged before exposureto. thelight beaintobe recorded.' The.' beaniirommirror i2 is projected'onto the coating l5 through a nar.- row slit in a .metalbarsi mounted on insulate ing supports in close proximity to coating l5. A high voltage D. C. source t8. has. itsitermin'als connectedto bar il and cylinder' It' respectively. The voltage is." preferably above 10190" volts.' but below the breakdownvalueof 'thespace between thelbar andthe cylinder. Theshape of tliebar is such as to concentrate a.strongjelectric'eld through. coating l5 in a-path beneath -thelslitin the bar. As the uncharg'ed' surface of coatin'g |i passes the slitA the lightlbeam will illuminate a spot in this path of higlflV electric iieldand. the resulting conductivity in' that spot" will allow a charge to flow from the metal cylinder iillto the outer surface of the coating. This.' chargebecomes trapped on Vthe surface as ythecoating areas progressively passbeyond the slit. This produces a resident charged line or graph of the'position oi the light spot; The line picks .up powder as it passes the dusting chamber whilev the uncharged background remains clean. Results can be' obtainedV with either the positive. or' negative D; C. terminal connected tothe bar fl'l, buti't is deslrableto use the polarity which'will'c'ausethe greatest powder deposit on. the chargedv graph line; For example, resin powdersoften carry negative charges, so they adhere best'toa positive graph line. Inthis case bar iT should be connected' to' the negative pole of the D; C. source, thereby creating a positive graph line.

When the method and. apparatus4 of'Figure is used it is possible to use a. graph scale and indicia printed' on` the surface of coatingv l5 in insulating ink as described in Carlson. Patent '2,357,809 granted September 12, 1944. (Figure-10).

rIghe insulating lines become frictionallyY charged by brush 384 andsince they are not photoconduc- Ative'they are not. discharged by lainpii- They thereforea'ttract powder duringdustingto give a visible scale which is transferred to the paper tape along with the. graph curve.

Figure 6A illustrates am'odied constructionof recording. meter. The photoconductive element 49. is in stripform. It may comprisea metal foil strip coated with a Alayer of photoconductive insulating material, f a self-supporting band of vphotoconductive insulating material, or a paper tape impregnated' with such material. For example paper impregnated with anthracene, as described in Carlson Patent 2,297,691, is suitable. This is unwound from a roll'Et and passes over a revolving-metal drums! then around a pair of parallel flanged wheels 52 and finally between a pair of driven rollers 53 to the outside of the casing 59- of the meter. A ldriven rotary charging brush 55 applies a. frictional electric charge to the band as it starts around drum 5i. YPosiioned above drum' 5! is a partition 55 having a narrow slitv 5'! `therein extending along the top edge. of the drum. A pair of electric indicating meters 58 and 59 are mounted above the partition with their pointer arms Sli and @i extend- .ing acrossthe slit. An electric lamp 8| is mounted above the pointers and illuminates the vslit 1 casting a narrow band of light across the width of 'photoconductive tape @Si except where the pointers St and 5l produce shadows. The tape is thereby electrically discharged by the light ex" cept where the pointer shadows fall. These shadows therefore describe graph curves on the tape as it moves around the drum. The tape then passes down under the rims of flanged parallel wheels 52 and up again to the driven tension rolls 53. A mass of electroscopic powder 62 rests in the trough formed by tape il@ as it passes under the wheels 52 is rolled or tumbled by the tape as it moves. (See also Figure 7.) A line of powder 62 will adhere to each of the two charged graph curves described by pointers @El and 6i rendering the record visible. The tape may be printed with suitable indicia and scales to aid in reading the graph.

A roll of moistened paper 53 is mounted in a casing Sli adjacent rolls and the paper is fed between these rolls in contact with the graph surface of tape dei. rThis paper carries water or other solvent into contact with the powder lines to partially dissolve them' and thereby them permanently on the tape. Some of the dye will be transferred to paper @3 affording a duplicate record, in reverse, of the graph. If alcohol soluble powders such as dyed zein, dyed ethyl cellulose or Vinsol resin are used the paper is moistened with alcohol, alcohol-water mixc tures or other suitable organic solvents such as butanol. A pad 55 in casing Gf! is also moistened with the solvent. An open container S53 of hygroscopic material such as calcium chloride is mounted in the meter casing to dry the air.

Figure 8 shows another solvent-hiring means for .powders which are dissolved or at least rendered adhesive by solvents. This can be substituted for the heat-fixing means 3l in the machine of Figure 1 or the solvent-fixing means $3 in the machine of Figure 6. It comprises a chamber [i6 insulated by double walls E5? and the bottom t8 of which comprises a reservoir for a solvent 69. A resistance heating element "ab is located in the reservoir for vaporizing the solvent. The chamber is closed except for two horizontal slits at opposite edges to permit paper tape 'i (or di!) to pass through the chamber above the liquid level. Sufiicient solvent condenses on the relatively cold tape as it passes through the chamber to partially dissolve a soluble powder image or graph thereon. When the tape leaves the chamber the solvent evaporates leaving the image xed to the paper.

Figure 9 shows a modified chamber which acts f powder on paper strip 90.

in much the same Way. The tape 3| passes 'around a metal roller 'Il mounted in the mouth of a thermally insulated reservoir 12 containing solvent absorbed in a mass of porous or fibrous material 'I3 in which is embedded a resistance heater '14. The powder image is on the outside face of tape 3| to avoid contact with roll 1|. The roll ll being colder than the inside of the reservoir aids in the condensation of solvent on paper tape 3l.

Ordinary alcohol, water, naphtha and other los boiling solvents can be used but to reduce evaporation losses and to obtain greater condensation on the tape it is desirable to use a solvent of medium or high boiling point such as butanol, butyl lactate, octyl alcohol, butyl Cellosolve, Carbitol,l diethyl Carbitol, butyl Carbitol, C-arbitol acetate and butyl Carbitol acetate. These are all of sufficient volatility to dry from thin lms in a short time.

While the photoconductive insulating coating is shown applied directly to the cylinder surface in Figures 1, 2, 4 and 5 it can also be applied to a thin lmetal cylinder which can be attached to a supporting drum, or a metal foil or plate which can be wrapped-around the drum.

Sulfur, anthraceneand anthraquinone are suitable photoconductive insulating materials, although a number of other materials can also be used.

Figure 10 shows a completed recording made according to the method described herein. The recording represents a completed graphic record after transfer 'and fixing of a resin developing The rulings 9| and graph curve 92 are fused resin powder transferred from the developed image on the photoconductive coating. The rulings ywere originally formed as printed insulating lines on the coating. The charged coating was passed under a slit across which the shadow of lan ammeter needle was cast. Upon development the powder adhered to the graph line and to the insulating rulings, after which transfer to the paper strip Sii was made.

While the present invention has been described as applied to recording meters it is contemplated that the invention, apparatus and methods `and parts thereof may be more widely applied in electrophot-ography, facsimile receiving systems and other fields and it is intended to cover the invention broadly within the spirit and scope of the appended claims.

It is obvious that the shadow arrangement of Figure 6 may replace the mirror beam arrangements of Figures 1 and 5 and vice versa, if desired.

What is claimed is:

l. A graphic recording machine comprising a conductive cylinder, a drive for continuously rotating said cylinder past five stations arranged in order about said cylinder, a coating of photoconductive insulating material on the outside of said cylinder, a discharging device vat the first of said stations for discharging any electric charge on said coating as said cylinder rotates past said device, an indicating instrument at the second of said stations having a moving element yand a light source co-operating therewith to project a beam of light onto said coating which varies in position across said coating with variations in the position of said moving element, a field producing device also at said second station for creating an electric eld through said coating at points where said coating is illuminated by said light beam, a dusting device at the third of said stations for depositing powder on said coating, a transfer device at the fourth of said stations for rolling a band of sheet material against said coating to transfer deposited powder t-o said band, and a cleaning device at the fth of said stations for cleaning said coating.

2. A graphic recording machine for continuous recording, said machine comprising, in combination, a conductive support having a substantially smooth surface, drive means for moving said support in a closed path through la cycle of positions, a layer of p'hotoconductive insulating material overlying said substantially smooth support surface in contact therewith, charging means -in one of said' positions for applying a substantially uniform electrostatic charge to the outer surface of said layer of photoconductive insulating material, light beam projecting means in a subsequent position in said cycle for traversving said layer with a light beam and condition responsive means for m-odifying said light beam in accordance with la condition to be recorded, a developing device in a position in said cycle subsequent to the position of said light beam projecting means for continuously applying a finelydivided electrostatically-attract'able material to the outer surface of said layer of photoconductive insulating material to deposit said electrostatically-attractable material on the areas of said layer which remain electrically charged, and a transfer device in a position in said cycle subsequent to the position of said developing device for continuously feeding a band of record paper against the outer surface of said layer Aof photoconductive insulating material to transfer said electrostatically-attractable material to said band of record paper.

3. In combination, means for supporting a band of sheet material having a length greatly eX- ceeding its width, at least the surface of said band comprising photoconductive insulating material, drive means for feeding said band lengthwise through a series of positions, charging means in one of said positions for applying a substantially uniform electrostatic charge to the surface of said band, light beam projecting means in a subsequent position in said series of positions for traversing said band with a light beam and condition-responsive means for modifying `Said light beam in accordance with :a condition to be recorded, a developing device in a position in said series subsequent to the position of said light beam projecting means for continuously applying a finely-divided electrostatically-attractable material to the surface of said band to deposit said electrostatically-attractable material on the areas of said band which remain electrically charged and thereby develop a visible graph on said band.

4. In combination, means for supporting a band of insulating material, means for feeding said band past electrostatic charging means and past a meter indicator to apply an invisible electrostatic graphic recording to said band in accordance with the condition indicated by said meter indicator, means for feeding said band downwardl;rvv then upwardly to form a, channel therein, and a powder in said channel for developing said electrostatic graphic recording.

5. The method of graphic recording which comprises applying an electrostatic image on a layer of sheet material and developing said electrostatic image which comprises forming a channel of said sheet, with the surface carrying said 'image concave, and tumbling a powder mass including electroscopic powder particles over said concave surface by moving said layer to vary the inclination to the horizontal cf various .portions of said surface.

CHESTER. F. CARLSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 572,699 Dunn Dec. 8, 1896 625,541 Cole May 23, 1899 1,065,684 Hesse June 24, 1913 1,308,904 Hopkins July 8, 1919 1,451,080 Mintrop Apr. 10, 1923 1,713,226 Hall May 14, 1929 1,805,197 Wood May 12, 1931 1,828,328 Legg Oct. 20, 1931 2,144,999 Frickett Apr. 26, 1938 2,297,691 Carlson Oct. 6, 1942 2,325,086 Vore July 27, 1943 2,328,461 Keinle et al Aug. 31, 1943 2,357,809 Carlson Sept. 12, 1944 2,396,833 Dhumy Mar. 19, 1946 

